基坑开挖卸载对下部地铁的作用分析

Research on the effect of unloading by pit excavation on subway

随着城市建设的高速发展,越来越多的基坑开挖工程处于既有地铁上方,由于上部的卸载作用,对下方既有地铁会带来一定的影响。宁芜改线项目基坑工程位于南京地铁的正上方,坑底距地铁顶的距离仅为7.5m,基坑开挖对地铁影响的分析与计算成为该工程的关键之一,文章建立了该基坑工程的数值分析模型。计算结果与实测结果的分析表明,基坑开挖对开挖面以下土体具有显著的垂直方向卸荷作用,带动土体中的地铁产生位移,同时基坑开挖卸荷的速度和方式是直接影响既有地铁变形的关键因素。所得成果可为优化设计和施工提供有益的参考,为类似工程提供借鉴。

With the rapid development of urban construction, more and more excavation works will be located on the top of the existing subway, and the unloading effect of the upper part have some impact on the existing subway below. The excavation work in Nanjing-Wuhu line changing project is just above the Nanjing sub- way. The distance between the bottom of the pit and the tunnel roof is only 7.5 m, so the analysis and calcu-lation of the effect of excavation on the subway becomes one of the key issues of the project, lor which a nu- merical model of the excavation is establisheck The computing and testing results show that the excavation leads to significant unloading effect on the soil below in the vertical direction, and results in the displacement of the tunnel in the soil. The rate and the way of the unloading of excavation are key factors leading to the de- formation of the subway. The research results can be provided to optimize the design and construction of the project and be a usful reference for similar projects.